This application relates generally to the field of batteries. More specifically, this application relates to element sleeves for pro-assembly of battery plates into cells having a desired compression state.
Lead-acid batteries use electrochemical materials, namely materials that produce electrical energy when exposed to certain electrolytes, to generate electrical current. In lead-acid batteries, lead is formed into plates or strips that are soldered together to form positive and negative electrodes. The positive and negative electrodes are interleaved to make up a complete battery cell. Separators are placed between the electrodes, and the complete cell is placed in a container along with other cells connected, in series or parallel, to provide a battery having the desired current and voltage capabilities. The electrolyte is placed in the container with the cells.
Lead-acid batteries use reactive sponge lead for the negative electrode, lead dioxide for the positive electrode, and dilute sulfuric acid for the electrolyte. During discharge of a lead-acid battery, the electro-chemical material is converted into lead sulfate by the acid, producing an electric charge. The amount of lead sulfate formed on the plates and the amount of acid lost from the electrolyte are in exact proportion to the rate of discharge. The reverse action takes place when the battery is recharged. Lead-acid batteries are typically classified by the manner in which the electrolyte is stored with in the battery. For example, lead-acid batteries include: (1) flooded lead-acid batteries; (2) gel lead-acid batteries; and (3) absorbed glass mat (hereinafter AGM) lead-acid batteries.
Flooded lead-acid batteries provide electrolyte to the plates in a liquid form. Gel lead-acid batteries provide electrolyte to the plates in a gelatinous state. AGM batteries provide electrolyte to the plates saturated in absorbent glass mats. AGM batteries are normally sealed, but they often times includes a valve that allows the escape of gas if the internal pressure exceeds a predetermined value. In this configuration, AGM batteries are also known as valve regulated lead acid or VRLA batteries.
The plates within an AGM battery are typically arranged so that they alternate in charge to form the battery cell. The absorbent glass mats separate the plates from adjacent plates to electrically insulate each plate from adjacent plates. The absorbent glass mats also provide multiple gas channels between the plates through which oxygen can migrate from the positive electrode when generated there to the negative electrode where it can be recombined with hydrogen, according to the oxygen cycle.
The battery cell, namely the plates and the separators, are maintained under compression to provide constant contact between the plates and the separators, respectively. Thus, AGM batteries require a state of constant compression of the plates and separators in each cell in order to function properly. The required compression is conventionally achieved by assembling the cell components into a stack having a given thickness, physically compressing the cell stack, and inserting the compressed cell stack in a battery case which is sized, relative to the size of the stack, to maintain the components of the cell stack under compression. Thus, the battery case is a stressed structural member of traditional AGM batteries and provides the required rigidity to the cells to maintain the necessary compression. However, this conventional method of using the battery case as a stressed member has numerous disadvantages.
Accordingly, the present invention provides an element sleeve, which not only provides the required structural and rigidity to the battery cell, but also aids in the assembly of the battery cell and the battery.
It is an object to provide an element sleeve for a compressible stack of battery elements. The element sleeve has a body defining a cavity for receiving the compressible stack of battery elements. The cavity has a height that is smaller than an uncompressed height of the compressible stack of battery elements by about 5% to 50%. A means compresses the compressible stack of battery elements to about the height of the cavity.
It is yet another object to provide a battery cell having a plurality of positive plates each having a positive lug, a plurality of separators, and a plurality of negative plates each having a negative lug. The positive plates, separators, and negative plates are configured into a compressible stack. A casing receives the compressible stack. The casing has an interior height smaller by about 5% to 50% than an uncompressed height of the compressible stack. A cover mated with the casing compresses the compressible stack to about the interior height of the casing.
It is another object to provide an absorbed glass mat lead-acid battery. The battery has one or more battery cells connected to one another in series and/or parallel to provide a predetermined current capability and a predetermined voltage capability. The battery cells each have a plurality of positive plates, a plurality of absorbed glass mat separators and a plurality of negative plates configured into a compressible stack. The compressible stack is compressed in a casing by a cover to about an interior height of the casing. The interior height of the casing is smaller than an uncompressed height of the stack by about 20%.
The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.